Hill's metal plate

Vyse
There once was a chap by the name of Colonel Howard Vyse. It was during the late 1830's that he made himself known through the exploration of the Great Pyramid. Naturally, by 'explore,' I in fact mean 'explode.'

Vyse liked to blow things up.

It was his gratuitous use of dynamite which won him renown, rather than any of his discoveries. Which, as we will see, was probably a good thing, in an odd sort of way.

The two star-shafts in the King's Chamber were first recorded in 1636 by a Dr. John Greaves (for further discussion on the shafts see the Great Pyramid of Giza node). Only in 1837 were they ever properly examined by Vyse and two aides, James Marsh and John Perring.

Discovery
Living in Cairo at the time was Mr J. R. Hill, who was also a member of Vyse's crew. He was ordered to clear the mouth of the southern shaft of the King's Chamber, at the point where it emerges from the Pyramid (102nd level). Hill was instructed to use dynamite, and as such was responsible for the enormous vertical scar which survives on the southern face to this very day.

After several days of blasting, on May 26, Hill extracted a metal plate measuring 12" x 4" x approx 0.125" from the masonry.

Vyse was quite excited by the discovery, and proceeded to proclaim it as the 'oldest piece of wrought iron known.' In Vyse's book Operations carried out at the Pyramids of Gizeh: With an account of a Voyage into Upper Egypt and Appendix, 1937, Hill had the following to say:

This is to certify that the piece of iron found by me near the mouth of the air-passage, in the southern side of the Great Pyramid at Gizeh, on Friday, May 26, was taken out by me from an inner joint after having removed by blasting two outer tiers of the stones of the present surface of the Pyramid; and that no joint or opening of any sort was connected with the above mentioned joint, by which the iron could have been placed in it after the original building of the Pyramid. I also shewed the exact spot to Mr. Perring, on Saturday, June 24th.

Both Perring and Marsh, civil engineers, certified that the iron must have been inserted the joint during the original building of the Pyramid, and could not have been inserted afterwards.

Doubt
Vyse sent the plate, bundled with the testimonies of Hill, Perring and Marsh, to the British Museum. Since that date the authenticity of the plate has been debated, for the following reasons:

The date. 2500BC, the generally accepted dating of the Great Pyramid (all of the Egyptian pyramids - it's called the Pyramid Age), is a few millennia shy of the Egyptian Iron Age. If the artifact is authentic, either the Pyramid or Iron Age will have to be adjusted.

Vyse's Credibility. Vyse carried out an extensive survey of the Relieving Chambers above the King's Chamber. His journal is suspiciously empty of specific details for that date, however on the following day, with witnesses present, a set of 'quarry marks' were immediately apparent. The validity of these marks has been thoroughly criticized, over three points.
The first, as noted by Joseph Jochmans, is that:

The perspective and angles at which the inscriptions were made shows that they were painted not by the quarry masons before the blocks were moved, but rather by somebody working in the cramped quarters of the chambers after the blocks had been placed in the Pyramid.

Jochmans goes on to note that 'quarry marks' would serve no purpose after the fact, and 'clearly they were added by someone else...'

The hieroglyphs themselves are quite inconsistent. There are terms used that do not come into use for another thousand years, and yet others from later dates. There are grammatical errors, such as the symbol for 'good' being used where 'eighteen' is meant. These were first noted by Samuel Birch, an ancient Egyptian language expert (although noone seems to care, the name of the preferred builder, Khufu, appears in the text, and it is therefore used as evidence for the dating of the Great Pyramid).

Finally, the symbol used to represent 'Khufu' is incorrect, an error that appeared identically in Materia Hieroglyphica and Voyage de l'Arabie Petree, the only two hieroglyph references available to Vyse at the time.

Analysis
Sir W.M. Flinders Petrie examined the plate in 1881, and in his publication The Pyramids and Temples of Gizeh, had this to say:

Though some doubt has been thrown on the piece, merely from it's rarity, yet the vouchers for it are very precise; and it has a cast of a nummelite on the rust of it, proving it to have been buried for ages beside a block of nummelitic limestone, and therefore to be certainly ancient.

This was not enough for the Egyptological heads at the time. 108 years later, in 1989, a fragment of was examined again by Dr M. P. Jones (of the Mineral Resources Engineering Department at Imperial College, England), and Dr Sayed El Gayer (of the Faculty of Petroleum and Mining in Suez University, Egypt), who gained his Ph.D. in extraction metallurgy. Their joint paper was submitted to the Journal of the Metallurgy Society, and can be found in Vol. 23.

El Gayer and Jones confirmed the following:

The nickel content is far less than 7%, thereby confirming that it is not meteoritic iron - certainly man-made.

It had traces of gold on one face. There has been speculation that the artifact was 'gold-plated, and that this gold may have been an indication that this... was held in great esteem when it was produced.' It should be noted that the shaft it was discovered in pointed directly at the constellation of Orion/Osiris, and is believed to be extremely important to the original purpose of the Pyramid.

According to El Gayer and Jones' text:

It is concluded, on the basis of the present investigation, that the iron plate is very ancient. Furthermore, the metallurgical evidence supports the archaeological evidence which suggests that the plate was incorporated within the Pyramid at the time that the structure was being built.

Again, the Egyptologists disputed the origins of the plate. According to the British Museum, the findings were 'highly dubious.' It is unlikely that the truth will ever be revealed, or indeed recognized if it is. Such is the nature of those at the head of the archaeological community, and the probable fate of discoveries in years to come.

Sources:
Operations carried out at the Pyramids of Gizeh: With an account of a Voyage into Upper Egypt and Appendix, 1937, Colonel Howard Vyse
'Metallurgical Investigation of an Iron Plate found in 1837 in the Great Pyramid at Giza, Egypt,' Journal of the Metallurgy Society Vol. XXIII
The Pyramids and Temples of Gizeh, 1883, Sir W.M. Flinders Petrie
Discussions in Egyptology Vol. XIV
Keeper of Genesis, 1996, R. Bauval & G. Hancock
The Search for Ancient Egypt, 1992, J. Vercoutter